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Kai Wu - One of the best experts on this subject based on the ideXlab platform.
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the effect of Discharge Area variation on stochastic characters of pd magnitude
IEEE Transactions on Dielectrics and Electrical Insulation, 2017Co-Authors: Kai Wu, Yongpeng Meng, Yonghong Cheng, Ju TangAbstract:Surface charges generated by previous Discharges at the solid-gas interface in a void can affect the characteristics of subsequent ones. In this paper, the effect of Discharge Area variation on the stochastic characters of partial Discharge (PD) magnitude was investigated by changing the void size. It is found that the uniformity of PD magnitude increased when void diameter was reduced. In order to clarify this, the corresponding Discharge Area variation was obtained by Pockels effect of Bismuth Silicon Oxide (BSO) crystal. As void diameter became smaller, due to the limitation of cavity walls, the fluctuation of Discharge Area became weaker, and hence the uniformity of PD magnitude increased. Besides, the result that the fluctuation of PD magnitude decreased when PD void height became larger was obtained. Considering the safety of BSO crystal, surface charge distribution was not measured by experiment for this case. Instead, a simulation model was constructed to obtain it. As a result, Discharge Area became larger when void height increased. According to this, it is inferred that the expanding of Discharge Area may be affected by cavity walls in the experiment. Therefore, the changing tendency of the uniformity of PD magnitude with the void height can be explained when the void Area remained unchanged. These results suggest that the variation of Discharge Area can affect the stochastic character of PD magnitude and further investigation is needed to clarify the PD mechanism.
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Effect of void Area on PD magnitude uniformity
2013 Annual Report Conference on Electrical Insulation and Dielectric Phenomena, 2013Co-Authors: Kai Wu, Yongpeng Meng, Yonghong ChengAbstract:Accumulated surface charges at the interface between solid dielectric and gas, resulting from former Discharges plays an important role in the characters of subsequent ones during the partial Discharge (PD) sequences. Specifically, it is assumed that variations in PD magnitude are associated with the Discharge Area. In our previous research, it was found that the diameter of Discharge Area can reach up to 1.5 mm due to the dielectric barrier. Based on this, different variation degree of Discharge Area was obtained via changing the void Area in this paper. When the size of void was larger (diameter 5.0 mm), streamer could spread freely after it landed on the interface, so the Discharge Area varied in a large range, leading to the intense fluctuation of Discharge magnitude. After the void diameter was reduced to 1.5 mm, the variation range of Discharge magnitude is restricted by the void edge. As the void Area became much smaller (diameter 0.7 mm), the uniformity of Discharge magnitude increased.
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effects of Discharge Area and surface conductivity on partial Discharge behavior in voids under square voltages
IEEE Transactions on Dielectrics and Electrical Insulation, 2007Co-Authors: Kai Wu, Tatsuki Okamoto, Y SuzuokiAbstract:The transitions of partial Discharge (PD) behavior with aging in a void under ac voltages with sine wave and square wave were observed. The transition of the PD magnitude with aging under square wave showed the same tendency as that under sine wave. Moreover, the experimental results also showed some distinctive characteristics of PDs under square voltage (e.g. more than two pulses after the voltage rise time and their transition with aging). These phenomena were explained in terms of the effect of Discharge Area and the change in surface condition due to PD degradation
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the contribution of Discharge Area variation to partial Discharge patterns in disc voids
Journal of Physics D, 2004Co-Authors: Y Suzuoki, Kai Wu, L.a. DissadoAbstract:Experimental ac partial Discharge (PD) patterns are presented for a disc-void (Area greater than length) with metal surfaces, one metal and one insulating surface, and with both surfaces insulating. These patterns indicate that the portion of the surface over which the charge is deposited (Discharge Area) plays an important role in producing the fluctuations in Discharge magnitude commonly observed for such voids. A simulation model for PD patterns in voids is presented, which expressly includes the effects of the charge distribution left on the void surface by consecutive PDs. This model defines two factors that control the PD propagation. These are: a minimum field required to maintain the Discharge within an existing surface path Ein and a minimum peripheral field required to extend the Discharge path Ep. There is also one other factor, the occurrence probability that controls the incidence of the PD. It is shown that the model gives a variation in PD magnitude throughout the active region of phase without any stochastic factors, i.e. when only variations in the Discharge Areas are allowed for, but that in order to reproduce the typical (turtle-like) PD patterns observed for the disc-void with insulating interfaces the occurrence probability and surface conductivity have to be included. The current model is compared to previous models and the relationship of the model factors to the change of PD patterns with ageing is briefly discussed.
L.a. Dissado - One of the best experts on this subject based on the ideXlab platform.
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the contribution of Discharge Area variation to partial Discharge patterns in disc voids
Journal of Physics D, 2004Co-Authors: Y Suzuoki, Kai Wu, L.a. DissadoAbstract:Experimental ac partial Discharge (PD) patterns are presented for a disc-void (Area greater than length) with metal surfaces, one metal and one insulating surface, and with both surfaces insulating. These patterns indicate that the portion of the surface over which the charge is deposited (Discharge Area) plays an important role in producing the fluctuations in Discharge magnitude commonly observed for such voids. A simulation model for PD patterns in voids is presented, which expressly includes the effects of the charge distribution left on the void surface by consecutive PDs. This model defines two factors that control the PD propagation. These are: a minimum field required to maintain the Discharge within an existing surface path Ein and a minimum peripheral field required to extend the Discharge path Ep. There is also one other factor, the occurrence probability that controls the incidence of the PD. It is shown that the model gives a variation in PD magnitude throughout the active region of phase without any stochastic factors, i.e. when only variations in the Discharge Areas are allowed for, but that in order to reproduce the typical (turtle-like) PD patterns observed for the disc-void with insulating interfaces the occurrence probability and surface conductivity have to be included. The current model is compared to previous models and the relationship of the model factors to the change of PD patterns with ageing is briefly discussed.
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Improved simulation model for PD pattern in voids considering effects of Discharge Area
2003 Annual Report Conference on Electrical Insulation and Dielectric Phenomena, 2003Co-Authors: K Wu, Y Suzuoki, L.a. DissadoAbstract:An earlier model for simulation of the phase-resolved pattern of partial Discharge (PD) showed that the range of PD magnitudes could be produced by a variation of Discharge Area. Here we present a further development of that model. When the field in the void exceeds a certain value E/sub c/, PD occurs and extends along the void surface. In the PD propagation, the fields in the Discharge paths and in the perimeter segments around the PD paths are reduced little by little by gradually changing the charge distribution. And the PD is terminated when the internal field in the PD path becomes lower than a critical value E/sub in/ and the field in the perimeter segments around the PD paths becomes less than another critical value E/sub p/. The simulation results became much closer to the actual PD patterns. And the large fluctuation of PD magnitude can be simulated even without consideration of any stochastic mechanisms. This model provides an approach to explain the transition of PD pattern in the aging process in terms of the change of surface condition.
Y Suzuoki - One of the best experts on this subject based on the ideXlab platform.
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effects of Discharge Area and surface conductivity on partial Discharge behavior in voids under square voltages
IEEE Transactions on Dielectrics and Electrical Insulation, 2007Co-Authors: Kai Wu, Tatsuki Okamoto, Y SuzuokiAbstract:The transitions of partial Discharge (PD) behavior with aging in a void under ac voltages with sine wave and square wave were observed. The transition of the PD magnitude with aging under square wave showed the same tendency as that under sine wave. Moreover, the experimental results also showed some distinctive characteristics of PDs under square voltage (e.g. more than two pulses after the voltage rise time and their transition with aging). These phenomena were explained in terms of the effect of Discharge Area and the change in surface condition due to PD degradation
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the contribution of Discharge Area variation to partial Discharge patterns in disc voids
Journal of Physics D, 2004Co-Authors: Y Suzuoki, Kai Wu, L.a. DissadoAbstract:Experimental ac partial Discharge (PD) patterns are presented for a disc-void (Area greater than length) with metal surfaces, one metal and one insulating surface, and with both surfaces insulating. These patterns indicate that the portion of the surface over which the charge is deposited (Discharge Area) plays an important role in producing the fluctuations in Discharge magnitude commonly observed for such voids. A simulation model for PD patterns in voids is presented, which expressly includes the effects of the charge distribution left on the void surface by consecutive PDs. This model defines two factors that control the PD propagation. These are: a minimum field required to maintain the Discharge within an existing surface path Ein and a minimum peripheral field required to extend the Discharge path Ep. There is also one other factor, the occurrence probability that controls the incidence of the PD. It is shown that the model gives a variation in PD magnitude throughout the active region of phase without any stochastic factors, i.e. when only variations in the Discharge Areas are allowed for, but that in order to reproduce the typical (turtle-like) PD patterns observed for the disc-void with insulating interfaces the occurrence probability and surface conductivity have to be included. The current model is compared to previous models and the relationship of the model factors to the change of PD patterns with ageing is briefly discussed.
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Improved simulation model for PD pattern in voids considering effects of Discharge Area
2003 Annual Report Conference on Electrical Insulation and Dielectric Phenomena, 2003Co-Authors: K Wu, Y Suzuoki, L.a. DissadoAbstract:An earlier model for simulation of the phase-resolved pattern of partial Discharge (PD) showed that the range of PD magnitudes could be produced by a variation of Discharge Area. Here we present a further development of that model. When the field in the void exceeds a certain value E/sub c/, PD occurs and extends along the void surface. In the PD propagation, the fields in the Discharge paths and in the perimeter segments around the PD paths are reduced little by little by gradually changing the charge distribution. And the PD is terminated when the internal field in the PD path becomes lower than a critical value E/sub in/ and the field in the perimeter segments around the PD paths becomes less than another critical value E/sub p/. The simulation results became much closer to the actual PD patterns. And the large fluctuation of PD magnitude can be simulated even without consideration of any stochastic mechanisms. This model provides an approach to explain the transition of PD pattern in the aging process in terms of the change of surface condition.
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A simulation model for PD patterns in voids with consideration of PD Discharge Areas
2000 Annual Report Conference on Electrical Insulation and Dielectric Phenomena (Cat. No.00CH37132), 2000Co-Authors: K Wu, T. Okamoto, Y SuzuokiAbstract:Based on the concept of the variable Discharge Areas of partial Discharges (PDs), a numerical calculation method was put forward to simulate the PD pattern. In addition the critical field for PD occurrence and the residual field, a new parameter E/sub s/ is introduced in this model to determine the Discharge Area. The probability for Discharge propagation along the surface is assumed to be determined by the field distribution on the surface. The Discharge propagation is terminated when the field in the perimeter segments of the PD paths on the surface becomes less than E/sub s/. By increasing E/sub s/ transition to swarming pulsive microDischarges (SPMD) is obtained. The rabbit-like PD pattern can be simulated if assuming surface conductivity of the void. Unlike the conventional simulation models that attribute the different PD behavior to the different probability for PD occurrence, this model might provide a new approach to connect the PD behavior with the surface condition of the insulating materials (e.g. the surface conductivity, the property for Discharge propagation on the surface etc.).
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effects of Discharge Area on pd patterns in voids
Conference on Electrical Insulation and Dielectric Phenomena, 1999Co-Authors: K Wu, Y SuzuokiAbstract:Unlike the case of a void with a larger diameter, no great reduction of PD magnitude was observed in a narrow void in the PD aging process. This suggested that the reduction of PD magnitude in a large void might be caused by the reduction of the Discharge Area of PD (or the region to which the carriers can diffuse instantaneously in a PD process). In a narrow void, the Discharge Area seems to be limited by the void size, and may not decrease much with the reduction of the time delay of PD in the aging process. Further experiments on a void between two metal surfaces also agreed with this consideration. Because the Discharge Area was always equal to the metal surface due to the high conductivity of the metal, the PD magnitude showed very small randomness, and the PD pattern did not change much with the reduction of the void size.
Grant Evenson - One of the best experts on this subject based on the ideXlab platform.
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Addendum to the Closure Report for Corrective Action Unit 339: Area 12 Fleet Operations Steam Cleaning Discharge Area, Nevada Test Site, Revision 0
2009Co-Authors: Grant EvensonAbstract:This document constitutes an addendum to the Closure Report for CAU 339: Area 12 Fleet Operations Steam Cleaning Discharge Area Nevada Test Site, December 1997 as described in the document Supplemental Investigation Report for FFACO Use Restrictions, Nevada Test Site, Nevada (SIR) dated November 2008. The SIR document was approved by NDEP on December 5, 2008. The approval of the SIR document constituted approval of each of the recommended UR removals. In conformance with the SIR document, this addendum consists of: • This page that refers the reader to the SIR document for additional information • The cover, title, and signature pages of the SIR document • The NDEP approval letter • The corresponding section of the SIR document This addendum provides the documentation justifying the cancellation of the UR for CAS 12-19-01, A12 Fleet Ops Steam Cleaning Efflu. This UR was established as part of a Federal Facility Agreement and Consent Order (FFACO) corrective action and is based on the presence of contaminants at concentrations greater than the action levels established at the time of the initial investigation (FFACO, 1996). Since this UR was established, practices and procedures relating to the implementation of risk-based corrective actions (RBCA) have changed. Therefore, this UR was reevaluated against the current RBCA criteria as defined in the Industrial Sites Project Establishment of Final Action Levels (NNSA/NSO, 2006). This re-evaluation consisted of comparing the original data (used to define the need for the UR) to risk-based final action levels (FALs) developed using the current Industrial Sites RBCA process. The re-evaluation resulted in a recommendation to remove the UR because contamination is not present at the site above the risk-based FALs. Requirements for inspecting and maintaining this UR will be canceled, and the postings and signage at this site will be removed. Fencing and posting may be present at this site that are unrelated to the FFACO UR such as for radiological control purposes as required by the NV/YMP Radiological Control Manual (NNSA/NSO, 2004). This modification will not affect or modify any non-FFACO requirements for fencing, posting, or monitoring at this site.
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Corrective Action Decision Document for Corrective Action Unit 151: Septic Systems and Discharge Area, Nevada Test Site, Nevada, Rev. No.: 0
2006Co-Authors: Grant EvensonAbstract:This Corrective Action Decision Document has been prepared for Corrective Action Unit (CAU) 151, Septic Systems and Discharge Area, at the Nevada Test Site, Nevada, according to the ''Federal Facility Agreement and Consent Order'' (FFACO) (1996). Corrective Action Unit 151 is comprised of eight corrective action sites (CASs): (1) CAS 02-05-01, UE-2ce Pond; (2) CAS 12-03-01, Sewage Lagoons (6); (3) CAS 12-04-01, Septic Tanks; (4) CAS 12-04-02, Septic Tanks; (5) CAS 12-04-03, Septic Tank; (6) CAS 12-47-01, Wastewater Pond; (7) CAS 18-03-01, Sewage Lagoon; and (8) CAS 18-99-09, Sewer Line (Exposed). The purpose of this Corrective Action Decision Document is to identify and provide the rationale for the recommendation of corrective action alternatives (CAAs) for each of the eight CASs within CAU 151. Corrective action investigation (CAI) activities were performed from September 12 through November 18, 2005, as set forth in the CAU 151 Corrective Action Investigation Plan and Record of Technical Change No. 1. Additional confirmation sampling was performed on December 9, 2005; January 10, 2006; and February 13, 2006. Analytes detected during the CAI were evaluated against appropriate final action levels (FALs) to identify the contaminants of concern for each CAS. The results of the CAI identified contaminantsmore » of concern at two of the eight CASs in CAU 151 and required the evaluation of CAAs. Assessment of the data generated from investigation activities conducted at CAU 151 revealed the following: (1) Soils at CASs 02-05-01, 12-04-01, 12-04-02, 12-04-03, 12-47-01, 18-03-01, 18-99-09, and Lagoons B through G of CAS 12-03-01 do not contain contamination at concentrations exceeding the FALs. (2) Lagoon A of CAS 12-03-01 has arsenic above FALs in shallow subsurface soils. (3) One of the two tanks of CAS 12-04-01, System No.1, has polychlorinated biphenyls (aroclor-1254), trichloroethane, and cesium-137 above FALs in the sludge. Both CAS 12-04-01, System No.1 tanks contain trichloroethane and 1,4-dichlorobenzene above ''Resource Conservation and Recovery Act'' toxicity characteristic limits. Based on the evaluation of analytical data from the CAI, review of future and current operations at the eight CASs, and the detailed and comparative analysis of the potential CAAs, the following corrective actions are recommended for CAU 151. No Further Action is the recommended corrective action for soils at CASs 02-05-01, 12-04-01, 12-04-02, 12-04-03, 18-03-01, and 18-99-09; and Lagoons C, D, F, and G of CAS 12-03-01. No Further Action with implementation of a best management practice (BMP) is recommended for soils at CAS 12-47-01 and Lagoons B and E of CAS 12-03-01. To be protective of future workers should the present scenario used to calculate FALs change, an administrative use restriction will be recorded per the FFACO agreement as a BMP. Close in Place with Administrative Controls is the recommended corrective action for Lagoon A of CAS 12-03-01. Based on the evaluation of analytical data from the CAI; review of future and current operations at CASs 12-04-01, 12-04-02, and 12-04-03; and the detailed and comparative analysis of the potential CAAs, the following corrective actions are recommended for the septic tanks at these CASs. No Further Action with implementation of BMPs is the recommended corrective action for septic tanks that do not contain potential source material from CAS 12-04-01, System No.4 (four tanks); CAS 12-04-02, System No.5 (six tanks); and CAS 12-04-03, System No.3 (four tanks). Clean Closure with implementation of BMPs is the recommended corrective action for the septic tanks from CAS 12-04-01, System No.1 (two tanks). The preferred CAAs were evaluated on technical merit focusing on performance, reliability, feasibility, safety, and cost. The alternatives were judged to meet all requirements for the technical components evaluated. The alternatives meet all applicable federal and state regulations for closure of the site and will reduce potential exposure pathways to the contaminated media to an acceptable level at CAU 151.« less
Yan Wu - One of the best experts on this subject based on the ideXlab platform.
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optical characteristics of the filamentary and diffuse modes in surface dielectric barrier Discharge
Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy, 2016Co-Authors: Ying Zhang, Jie Li, Nan Jiang, Kefeng Shang, Na Lu, Yan WuAbstract:Abstract Surface dielectric barrier Discharge (DBD) plasmas generally exhibits filamentary and diffuse Discharges at atmospheric air. The focus of this investigation is on the different optical characteristics and quantitative research about morphological features of two Discharge modes. The temporally and spatially resolved characteristics of Discharge phenomenon together with the gas temperature are presented with microsecond time scale. Discharge Area is estimated by the sum of pixels that equal to “1” in MATLAB software. The formation of diffuse plasma mainly depends on an increase of the ionization coefficient and a creation of sufficient seed electrons by the Penning effect at low electric fields. Accordingly, experimental measurements show that diffuse Discharge during the negative half cycle has good uniformity and stability compared with filamentary Discharge during the positive half cycle. The rotational temperatures of plasma are determined by comparing the experimental spectra with the simulated spectra that have been investigated. The plasma gas temperature keeps almost constant in the filamentary Discharge phase and subsequently increased by about 115 K during the diffuse Discharge. In addition, it is shown to be nearly identical in the axial direction. Non-uniform temperature distribution can be observed in the radial direction with large fluctuations. The plasma length is demonstrated almost the same between two Discharge modes.